Detect duplicate keys in configuration.yaml.

homeassistant/util/yaml.py

@@ -1,7 +1,7 @@
 """YAML utility functions."""
 import logging
 import os
-from collections import OrderedDict
+from collections import Counter, OrderedDict
 
 import yaml
 
@@ -36,7 +36,11 @@ def _include_yaml(loader, node):
 def _ordered_dict(loader, node):
     """Load YAML mappings into an ordered dict to preserve key order."""
     loader.flatten_mapping(node)
-    return OrderedDict(loader.construct_pairs(node))
+    nodes = loader.construct_pairs(node)
+    dups = [k for k, v in Counter(k for k, _ in nodes).items() if v > 1]
+    if dups:
+        raise yaml.YAMLError("ERROR: duplicate keys: {}".format(dups))
+    return OrderedDict(nodes)
 
 
 yaml.SafeLoader.add_constructor('!include', _include_yaml)

tests/util/test_yaml.py

@@ -0,0 +1,34 @@
+"""Test Home Assistant yaml loader."""
+import io
+import unittest
+
+from homeassistant.util import yaml
+
+
+class TestYaml(unittest.TestCase):
+    """Test util.yaml loader."""
+
+    def test_simple_list(self):
+        """Test simple list."""
+        conf = "config:\n  - simple\n  - list"
+        with io.StringIO(conf) as f:
+            doc = yaml.yaml.safe_load(f)
+        assert doc['config'] == ["simple", "list"]
+
+    def test_simple_dict(self):
+        """Test simple dict."""
+        conf = "key: value"
+        with io.StringIO(conf) as f:
+            doc = yaml.yaml.safe_load(f)
+        assert doc['key'] == 'value'
+
+    def test_duplicate_key(self):
+        """Test simple dict."""
+        conf = "key: thing1\nkey: thing2"
+        try:
+            with io.StringIO(conf) as f:
+                yaml.yaml.safe_load(f)
+        except Exception:
+            pass
+        else:
+            assert 0